Roof jack



w. R. GRACE Sept. 19, 1961 "VI'ENTOR a b0X-like body having an inlet opening in its bottom` Side and all outlet o enjn in its foTwa d side, a substantia]ly horizonta11y disp0sed, ertuTed )artiti011in the body(0ver1ying the i1'11et opening, a primary Shutter having* front and Tear edges arranged within the body to nor- :nally overlie and close the aperture il1the 1)artition and mea11s pivotany connecting the rear edge of the shutter in the body, the forward edge extending transversely of the outlet opening, a substantia11y vertical1y disposed secndary shutter arranged in the body to nortnally extend across and close the outlet opening a11d neans pivota1ly connecting the Secondaty shutter il the body on an axis intermediate and paralle1 With the top and bottom edges of the Said Shutter the botton1 edge of the Secondary shuttel' normauy occurting adiacent and Stopped by the forward edge of the primary shutter, a trigger iixed t0 and proiecting rearwardly fi'on1 the centfal portion o the Secondary Shutter, said prima;y shutter adapted t0 be pivoted upwardly and Tarvvatdly 't) an open )Sition and away from the Secondary Shutter by .the oW of air int0 the 'body thOugh the nlet opening whereby the Secondary Shutter iS f1 ee ^to piyot to a Substantially hofizontally disposed opel1 positi01 Said pri111ary Shutter engagilg the trigger upon upward movement to pivot and open Said secondary Shutter, said partition having an upwardly tumed sealing lip about the perinete1' of the aperture therein and Said 1)Timary Shutter having a Sea1- ing member Xed thereto to engage the lip when the shutter is iI1 its l10rl11al closed ;0Sitio11.

Refeences ce in the me 0f this patent UNTTED STATES PATENTS McMahan Dec z7, 1938 Pryne Apr 17, 19S6 Carrick Mar. 19 197 

